Question: What is the best placement for my navigation menus?

I can't decide whether I want to put my navigation menus across the top of my site, or down the side. Or perhaps if there's some other placement scheme which would work better than either of those. What do you suggest?

Answer

Aug, 2007: This answer has been slightly modified. The original answer gave examples of sites with different styles of navigation systems. This was a foolish thing to do, considering how often website designs change. Those examples have been removed.

The most important thing is consistency. The worst mistake you can make is to have your navigation scheme in a different place or orientation on every page. If you do this, your users will get frustrated and wander off instead of taking the time to look for the information/product they want.

The actual placement and orientation of the navigation options is partly a matter of personal taste, and partly a matter of what you want to do with the site. If you use a horizontal navigation menu, you've given yourself more width to use for your content. If, on the other hand, you use a vertical menu, you've cut into the space that might be used for content.